But the Wales international has endured a slow start to life at the Bernabeu, with injury preventing him from starring under Madrid manager Carlo Ancelotti.

Bale has only made three appearances for Madrid since making his switch from the Premier League.

And Redknapp said that Bale’s relationship with Portuguese superstar Ronaldo could prove the determining factor if his time in Spain is to be deemed a success,

“His relationship with Ronaldo is the key to it all, because if the football is going well then all the added stresses are a minor irritation and nothing more," Redknapp wrote in his new book, being serialised in the Daily Mail.

“His biggest test will be to step out of the shadow of Cristiano Ronaldo with confidence. That won’t be easy

“Ronaldo is a huge star at Madrid and will probably want to take nine out of 10 free-kicks - at least. Gareth will have to assert himself and that will require a strong mind. He has to think ‘I’m an £86million player’ and act like it, taking responsibility, claiming the ball when he fancies his chances.

"The one thing the club cannot provide for Gareth and Cristiano is a ball each - so they will need to work hard on that partnership because they are such similar players."

However, Queens Park Rangers boss Redknapp said dislodging Madrid’s main star from the spotlight could prove difficult for a player who will not enjoy the mass scrutiny attracted by playing at one of the game’s biggest clubs.

"When he goes it alone, has a shot, misses and Ronaldo starts throwing his arms up in the air ... he cannot, at that point, go into his shell and become this timid little creature,” Redknapp writes. “But it is not natural for Gareth to behave in an assertive way.

"Don’t get me wrong, he knows he is good ... he wouldn’t have fought so hard to get the deal done if he didn’t fancy his chances of living up to expectations in Madrid. Yet, equally, Gareth is a quiet lad, who spends time with his girlfriend and family. I’m not sure being in the same bracket as Ronaldo and Lionel Messi will suit him.

"He had a little trouble adjusting to the bigger environment of Tottenham after leaving Southampton and this is 10 times as great as that move. If I have a worry it is that I remember the days when Gareth’s confidence was draining fast at Spurs and there were genuine fears he might not make it ... he won’t like the attention a difficult start brings either. Gareth is a very private person and he won’t enjoy having every move scrutinised."